Structure Preserving Approximations of Conservative Forces for Application to Small-Body Dynamics

Approximation-based methods, such as the cubetree algorithm, have proven to be significantly faster than traditionalmethods for complex force evaluations near small irregular bodies. Suchmethods also hold the promise of simplifying the inclusion of experimental data to update the force model. However, the cubetree algorithm does not preserve intrinsic properties of the gravitational force such as continuity, divergence freedom, or exactness. These properties may be needed for trajectory optimization, for the use of geometric (e.g., symplectic) integrators for longterm propagation, and for other trajectory design problems. This paper presents several adaptive schemes preserving global continuity, exactness, or divergence freedom, and discusses the difficulties involved in preserving all of these properties globally.